Biological species characteristically expand as much as resources allow and predators, parasites, and physical conditions permit. When a species is introduced into a new habitat with abundant resources that accumulated before its arrival, the population expands rapidly until all the resources are used up. In wine making, for example, a population of yeast cells in freshly pressed grape juice grows exponentially until nutrients are exhausted or waste products become toxic. By exploiting fossil fuel energy to modify more and more of its environment to suit human needs, the human population effectively expanded its resource base beyond immediate requirements. This has allowed a population expansion similar to that of species introduced into extremely propitious new habitats, such as rabbits in Australia or Japanese beetles in the United States. While it took 10,000 lifetimes for the human population to reach 2 billion, today, during a single human lifetime, the population may soar from 2 billion to 8 billion. Reminiscent of the manner in which a micro-organism can proliferate when introduced into the nutrient layer of a petri dish, an exponentially expanding human population has colonized the terrestrial biomes of the Earth.

Similar patterns are present in our planet's loss of forests, topsoil, groundwater stocks, wildlife species, stratospheric ozone, and climate stability. Most of the transformations wrought by humanity during the past 10,000 years have occurred in our lifetimes, as we've altered our environment in increasingly significant and diverse ways. Human-induced modifications to planetary processes, including biogeochemical and hydrologic cycles, are now on a scale that rivals natural changes to the Earth.

Easter Island is located over 2,000 miles from the nearest population center, making it one of the most isolated places on Earth. Viewed from above, Easter Island's surface area of only 64 square miles appears as a miniscule speck in the comparative immensity of the Pacific Ocean.

Archaeological and linguistic evidence suggest that Easter Island's first inhabitants arrived from Polynesia around A.D. 400 to 800. When the Polynesian colonists landed after a long canoe voyage from East Polynesia, they probably discoverd an untouched paradise. Easter Island's subtropical location of 27° latitude south connotes a mild climate, while its volcanic origins indicate a source of fertile soil. The new arrivals probably found a subtropical forest of trees and woody bushes towering over a ground layer of shrubs, herbs, ferns, and grasses, to which the early settlers would also have added the plants and animals that they carried with them.

The extinction of the island’s animals was as thorough as that of the forest. Every species of native land bird went extinct; shellfish were overexploited. Porpoise bones disappeared abruptly from garbage heaps around 1500, since trees used for constructing seagoing canoes disappeared. Colonies of more than half of the seabird species breeding on the island or on its offshore islets were exterminated.

Isolated in the mid-Pacific, Easter Island exhibits various ingredients of societal collapse resulting from ecological neglect. As the descendents of the Polynesian settlers multipled unrestrained into a population numbering in the thousands, competing factions in the populous, complex society carved enormous Moai stone statues, which they erected on the seacoast far from the quarries. The forests were cut to provide logs for transporting the statues. Moai statue carving and transport intensified from 1400 to 1600 as the last stands of trees were hewn. Core sampling from the subsequent period indicates deforestation, soil depletion, and erosion leading to collapse of the island's society.

Did the islanders - recognizing their impending peril - stop quarrying, carving, and transporting Moai statues? No, and in the ensuing ecological disaster most of the island's inhabitants starved or were victims of vicious conflict. The heirs to folly on Easter Island could not escape the their fate: they lacked trees with which to construct canoes and flee into the ocean. The island population collapsed from a level of thousands to hundreds, and never recovered.

Easter Island could presage, in miniature, problems that have started to cascade on a planetary scale as our global population grows unrestrained at the level of billions. For example:

• Logging and conversion have shrunk the world's forests by as much as half.
• Some 9 percent of the world's tree species are at risk of extinction; tropical deforestation may exceed 130,000 square kilometers per year.
• Fishing fleets are 40 percent larger than the ocean can sustain.
• Nearly 70 percent of the world's major marine fish stocks are overfished or are being fished at their biological limit.
• Soil degradation has affected two-thirds of the world's agricultural lands in the last 50 years.
• Some 30 percent of the world's original forests have been converted to agriculture.
• Since 1980, the global economy has tripled in size and population has grown by 30 percent to exceed 6 billion people.
• Dams, diversions or canals fragment almost 60 percent of the world's largest rivers.
• Twenty percent of the world's freshwater fish are extinct, threatened or endangered.

Following over 3.5 billion years of the evolution of life on Earth, and the advent of agricultural domestication 12,000 years ago with the subsequent rise of literate urban civilizations about 5,000 years ago, our kind - the human species - has arrived at a critical historical juncture. A planetary civilization has started to emerge. The genesis of this new civilization is one of the most significant facts of our lifetimes.

What is unique to this contemporary historical condition is the change in the rate of cultural change. The evolution of the human species from its primate lineage spanned a period of millions of years. Prior periods of comparatively rapid cultural transformation - such as the European Renaissance and Industrial Revolution - spanned more than a century. But the rate of contemporary cultural change is so rapid and intense that it is happening within the extent of an individual's lifetime.

We consequently face a visionary challenge. Old forms of thinking, dogma and ideology - no matter how venerated or appropriate in the past - are dubious precedents for a successful transition to a viable planetary society.

But what of the alternate branch, Planetary Senescence?

The alternative possibilities for future human (and planetary) progression - Cosmic Evolution and Planetary Senescence - can be epitomized by analogy.

Cosmic Evolution For Cosmic Evolution, artifacts such as the Hubble Telescope and the International Space Station may represent a nascent technical planetary civilization reaching out into a new interstellar environment, analogous to air-breathing vertebrates that had earlier pioneered the transition from a marine habitat to continental surfaces.

Planetary Senescence For Planetary Senescence, the intensive energy and resource intemperance exemplified by contemporary entertainment and amusement centers could prove symptomatic of an ill-conceived, misguided investment of resources analogous to the Moai statues of Easter Island that now stand as mute sentinels, pertinent reminders of the naive folly of the complex society that formerly populated Easter Island.

We have virtually and simultaneously gained the ability to unlock the secrets of our Universe, as well as to self-destruct. Given a choice, Cosmic Evolution may be our most appropriate and desirable future. But given the facts, Planetary Senescence may be our eventual fate.